This invention relates to a videoscope employing an image sensor such as a charge coupled device (CCD), and especially relates to a dental scope used for a dental or oral use.
Recently, such a videoscope has been used for an examination or a medical care of an oral cavity in a dental clinic or in oral surgery. One type of such videoscope employs an optical fiber for guiding light rays as disclosed in Japanese laid open patent applications (Tokukaihei) 4-176436 and 4-285525, for example. Another type disclosed in Japanese laid open patent application (Tokukaisho) 62-246347 uses an optical fiber for guiding an image of the object to the image sensor such as CCD. The videoscope disclosed in Tokukaihei 4-176436 uses an optical system including lenses for guiding an image of the object to the image sensor.
Such a videoscope is required to be easy to handle with one hand, have a high quality image and an inexpensive price for wide use.
The prior art disclosed in Tokukaihei 4-176436 has an optical fiber for guiding light rays. This optical fiber should have a complicated shape fitting to a narrow space inside the videoscope, which also contains lenses and prisms for condensing or dispersing light rays. However, since an optical fiber is hard to bend in a small angle and is easy to break, it can hardly extend to the tip inner portion. It is also difficult to decrease the number of the components.
The videoscope of the prior art has another disadvantage in that it is not easy to handle since it has an optical fiber connecting a grip portion of the videoscope and an external light source box, in addition to an electric cable connecting the grip portion of the videoscope and an external video circuit. The optical fiber and the electric cable can be integrated into a cord in recent technology, but it is not enough to improve the difficulty in handling the videoscope.
Moreover, the videoscope of the prior art needs a long optical path including lenses or an optical fiber for transmitting a light image of the object to an image sensor. This complicated structure makes it difficult to reduce the size and cost of the video scope.
The present invention is aimed at a novel structure of such a videoscope that enables easiness of handling and an inexpensive price.